Coastal Aquifer Protection from Saltwater Intrusion Using Abstraction of Brackish Water and Recharge of Treated Wastewater: Case Study of the Gaza Aquifer

Coastal aquifers are threatened by saltwater intrusion (SWI), which leads to degradation of groundwater quality by raising salinity. SWI occurs due to human activities such as overabstraction or natural processes such as sea-level rise. SWI control can help in protecting coastal aquifers from deterioration. This paper presents a numerical study using the simulation of three-dimensional variable-density ground-water flow (SEAWAT) code to investigate and control SWI in Gaza aquifer, Palestine, considering overpumping due to population growth and sea-level rise. Application of different scenarios to investigate SWI in Gaza aquifer showed that the intrusion of the equi-concentration line at 35,000 ppm, which is the interface between freshwater and saline water that reached 3,177 m in 2010, were compared to the field investigation in 2010, and by 2055 it will increase to 3,186, 3,518, 5,619, and 6,523 m due to sea-level rise, reducing recharge, and overpumping (percentage changes of 0.29%, 10.74%, 76.87%, and 105.32%, respectively). The results reveal that the intrusion length will double in 2055, and overpumping is considered the main cause for such an increase. Three management scenarios were used to control SWI in Gaza aquifer, including the abstraction of brackish water, recharge of the aquifer using treated wastewater, and a combination of both. Brackish water abstraction led to retardation of SWI at 3.5 km; recharge using treated wastewater led to retardation of SWI at 3.6 km, but a combination of both scenarios led to a retardation of SWI at 3.7 km. The results revealed that recharging the aquifer using treated wastewater could retard intrusion of saline water more than abstraction of brackish water, while the combination of both scenarios gave a higher retardation rate for saline water toward the sea. Aquifer recharge using treated wastewater is considered an effective tool to control SWI and protect coastal aquifers from deterioration.